1. Field of the Invention
The present invention relates to a preformat method for a magnetic recording medium, a magnetic recording medium itself, and a magnetic recording and reproducing apparatus.
2. Description of Related Art
Various kinds of technologies aiming at a higher recording density have been put to practical use for the purpose of realizing capacity increase of a magnetic recording and reproducing apparatus. Japanese Patent Application Laid-Open No. 2001-134936 discloses a technology for using photolithography technique to form (record) on a master information medium preformat information patterns including a recovery pattern, a sector mark pattern, a servo information pattern and a code data pattern as concavity and convexity patterns of a magnetic film, and for using magnetic transfer technique to transfer (record) the preformat information patterns onto a slave information medium (which is hereinafter referred to as a magnetic recording medium). The recovery pattern is a pattern to be used for synchronizing a clock of a magnetic head when the magnetic recording and reproducing apparatus records/reproduces information; the sector mark pattern is a pattern indicating the beginning of a sector; the servo information pattern is a pattern to be used for detecting the relative position of a track on the magnetic recording medium with regard to the magnetic head; and the code data pattern is a pattern indicating a track position, a sector position and the like. The magnetic recording and reproducing apparatus reads such preformat information from the magnetic recording medium so as to perform a predetermined tracking operation.
The magnetic transfer technique mentioned above allows time required for recording preformat information (preformat time) to be significantly reduced in comparison with a case where preformat information is recorded on a magnetic recording medium by a conventional STW (Servo Track Writer). For instance, preformat time of a magnetic recording medium of 20 G bytes is approximately ten minutes in the STW method, while it is even shorter than ten seconds in the magnetic transfer technique. Consequently, they place high hopes on the aforementioned magnetic transfer technique as the de facto standard of a preformat method for a magnetic recording medium.
Since a device for pattern plotting such as an optical exposure device or an EB (Electron Beam) exposure device is under extremely little restriction of dimension and of costs in comparison with a magnetic disk device, it is possible to employ a device of high accuracy. In the magnetic transfer technique, for example, an NRRO of a spindle (Non Repeatable Run Out: non repeatable component, which is not synchronized with rotation due to a run-out error of a spindle rotary axis) or the like is detected and correction operations are applied to light for pattern plotting, electron beams or the like, so that patterns under little influence of the NRRO can be formed. A master information medium prepared by the magnetic transfer technique can therefore realize higher pattern accuracy in comparison with a medium prepared by a method using the STW.
One method of the aforementioned magnetic transfer technique is to record all the preformat information on a master information medium and to transfer the preformat information onto a magnetic recording medium by magnetic transfer.
In the above-mentioned method, however, the size of preformat information patterns to be recorded on a magnetic recording medium is decided by the size of patterns of a magnetic film which are formed on a master information medium, i.e., the wavelength of light or electrons outputted from an optical exposure device, an EB exposure device or the like. It is, therefore, difficult to form preformat information patterns smaller than patterns recorded by a recording head. Consequently, there arises a problem that a preformat efficiency (a ratio of preformat information in a magnetic recording medium (which is hereinafter referred to as an occupation ratio)) declines.